1. Field of the Invention
This invention relates to a red eye prevent control device in an automatic focus adjustment camera for preventing the red eye effect during flash photographing and a red eye prevent photographing method involving automatic focus adjustment.
2. Related Background Art
The red eye effect refers to the fact that in color photographing using an electronic flash unit, man's eyes are photographed in red or hold color. This effect occurs by the flash of the light emitting portion of an electronic flash unit passed through the pupil of an eye being reflected by the retina portion and the reflected light falling upon a film. There are a number of capillary vessels in the retina portion of the eye and the hemoglobin in the blood therein is red and therefore, the reflected light therefrom falls upon a film with a tinge of red.
It has been empirically found that it is under the following conditions that the red eye effect occurs conspicuously in a photograph.
1) When the environment of photographing is dark
The size of the pupil of man's eye is varied by the brightness of the environment, and when the environment is dark, the diameter thereof widens to about 7-8 mm. At such time, the quantity of light incident on the eye and the quantity of reflected light from the eye become great and therefore, as a matter of course, the red eye effect is liable to be conspicuous.
2) When the distance between the light emitting portion of an electronic flash unit and the optic axis of a photo-taking lens is short
The retina portion of the eye is considerably high in reflectance and at the same time, high in the directionality of reflection. Accordingly, when the distance between the light emitting portion of the electronic flash unit and the optic axis of the photo-taking lens is short and the three elements (the light emitting portion, the photo-taking lens and the eye) are in a positional relation in which the regularly reflected light from the retina is ready to intactly enter the photo-taking lens, red eye occurs strongly. That is, when the angle at which the eye of a person which is the object to be photographed looks at the photo-taking lens and the light emitting portion of the flash light source is a small angle less than a certain degree, red eye occurs without fail. Empirically, this angle is about 2-2.5 degrees. Accordingly, if the light emitting portion of the electronic flash unit is kept apart from the optic axis of the photo-taking lens, occurrence of red eye will be prevented, but this is limited by the distance from the camera to the object (hereinafter referred to as the object distance) and it is difficult to avoid red eye when the object distance is a predetermined value or greater.
So, a technique for preventing the red eye effect is known. For example, in psa JOURNAL, July, 1952, there is disclosed a method of accustoming an eye to a bright environment before photographing and emitting a flash with the pupil of the eye reduced to 3 mm or less, thereby preventing red eye.
In Japanese Patent Publication No. 58-48088, there is disclosed a technique in which irradiation by a preliminary illuminating lamp is effected before photographing for the time necessary for the pupil to close and the light emitting portion of an electronic flash unit is caused to emit light when the pupil has assumed approximately its smallest diameter, thereby effecting photographing.
Also, in Japanese Laid-Open Patent Application No. 58-9130, there is disclosed a method in which two flash discharge tubes are provided and one of them is caused to emit light preliminarily to close the pupil, whereafter the other discharge tube is caused to emit light, thereby effecting actual photographing.
The assignee of the present application has also filed red eye prevent control devices which have improved these prior arts as U.S. application Ser. No. 323,386 (filed on Mar. 14, 1989) and U.S. application Ser. No. 389,795 (filed on Aug. 4, 1989). The former application includes as an embodiment a camera as will be described hereinafter. The camera starts the detection of focus adjustment information for focusing a photo-taking lens to an object with the half depression operation of a shutter release button, and effects automatic focus adjustment on the basis of the detected focus adjustment information. Thereafter, with the full depression operation of the release button, pre-light emission for preventing red eye is effected by a flash discharge tube, and after the lapse of the time necessary for the pupil of a person who is the object to be photographed to be closed enough to prevent the red eye effect by the stimulus of the pre-light emission (the order of 0.75 second, and this time will hereinafter be referred to as the pupil reduction waiting time), the shutter is operated and main light emission for flash photographing is effected by another flash discharge tube or the same flash discharge tube.
Accordingly, in U.S. application Ser. No. 323,386, there has been the undesirable possibility that a time lag occurs during the time from the detection of the focus adjustment information until photographing is effected and an out-of-focus photograph is taken when the object moves during that time.